"You know, Trump claims to be a real tough guy, pushes people around. Hey, Donald, let's have a debate about the future of America," says the senator.

Bernie Sanders pulled no punches when he dropped by Real Time With Bill Maher on Friday night.

The Vermont senator and presidential hopeful said on the HBO show that he still wanted to debate the presumptive GOP presidential nominee and warned about Trump being elected president.

"You know, Trump claims to be a real tough guy, pushes people around. Hey, Donald, let's have a debate about the future of America," said Sanders.

On Friday, Trump said he decided he would not debate Sanders, since Hillary Clinton is in the lead for the Democratic presidential nomination.

Sanders then said he thinks Trump is "crazy" and that him winning the White House would be dangerous.

"This guy is a pathological liar, and I don't mean to be malicious, but that is just the damn truth," said Sanders. "And he would not only be an embarrassment, but a real danger to the entire world if he were to become president."

Sanders admitted combating Trump in the general election would be difficult.

I would not be honest if I said I figured it out yet because he is so unpredictable because he changes his mind all the time," said Sanders.

Maher ended the interview by telling Sanders not to give up with his bid, adding, "You're killing it."